fix: issue with color scheme in layout

[Meierschlumpf]

Homarr

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This fixes the bug that sometimes the whole screen is black and there are no colors. The reason was, that we only used the color scheme when signed in and otherwise it was not set. Now I use a cookie and when you log in it's set to that one saved for the specific user

[deepsource-io]

Here's the code health analysis summary for commits 6aa5adf..0a5ed13. View details on DeepSource ↗.

Analysis Summary

Analyzer	Status	Summary	Link
JavaScript	✅ Success		View Check ↗

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[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	39.24%	13626 / 34724
🔵	Statements	39.24%	13626 / 34724
🔵	Functions	35.53%	361 / 1016
🔵	Branches	70.69%	1228 / 1737

File Coverage

File	Stmts	% Branch	% Funcs	% Lines	Uncovered Lines
Changed Files
apps/nextjs/src/app/[locale]/layout.tsx	0%	0%	0%	0%	1-2, 4-7, 9, 11-14, 16-23, 25-28, 30-47, 49-54, 56-58, 60-69, 71, 73-84, 86
apps/nextjs/src/app/[locale]/_client-providers/mantine.tsx	0%	0%	0%	0%	1, 4, 6-7, 9-11, 13-14, 16-23, 25-26, 28, 30-40, 42, 44-48, 50-52, 54-60, 62-72, 74-80, 82-83, 85-87, 89-93
packages/auth/callbacks.ts	90.78%	92.85%	100%	90.78%	89, 92-95, 97-98
packages/common/src/cookie.ts	20%	100%	0%	20%	5-7, 9-17, 19-20, 23-24

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